DIY Presidential Teleprompter:
How does a teleprompter work? A teleprompter is a transparent mirror at an angle over a display.
The magic of the teleprompter is the beamsplitter, which is highly transparent so you can record straight through it.
When recording through the mirror, if you don’t want reflections from other lights, make sure to drape a black cloth over the camera.
When your not recording through the mirror, the reflection of the script is invisible on the backside so only the speaker can see it.
This makes it so the person giving the speech can still see and interact with the audience.